The instant invention relates to a process for preparing capped polyoxyalkylene polyols.
Etherification or capping of a polyoxyalkylene compound having at least one terminal hydroxyl group has to date generally been effected by reacting the polyoxyalkylene compound with an alkali metal or its hydride such as sodium metal, potassium metal, sodium hydride or potassium hydride or sodium or potassium methoxide followed by reaction with an organic halide. Reaction with sodium methoxide is followed by removal of methanol produced by the reaction of the hydroxyl end groups with the alkali metal methoxide. However, the reaction eventually stops due to an equilibrium shift that does not favor methylation of the polymer. If the polymer is treated with methyl chloride at this point, the product would not be fully methyl capped.
If the polymer is reacted with sodium hydride rather than sodium methoxide prior to reaction with the organic halide, problems are presented due to the extremely high reactivity of the sodium hydride.
U.S. Pat. No. 3,507,923 discloses a method of capping allyl endblocked oxyalkylene polymers by reacting the polymer with sodium or potassium methylate (methoxide) followed by reaction with methyl chloride.
U.S. Pat. No. 4,046,702 describes treatment of polyoxyalkylated alcohol with sodium hydride or sodium methoxide prior to sulfating while U.S. Pat. No. 3,954,639 discloses treatment of an oxyalkylated alcohol or phenol with sodium hydride prior to sulfating.
U.S. Pat. No. 3,231,619 discloses the use of sodium hydride and sodium alkoxides among many other sodium compounds as a catalyst for oxyalkylating.
Accordingly it is the purpose of the instant invention to provide a method for purification or capping of polyoxyalkylene compounds wherein 95 to 100 percent capping is achieved by an easily controllable reaction in a relatively easy economical and safe manner.